The present invention relates to a liquid crystal display device, and more particularly to a technique which is effectively applicable to a direct backlight used in a liquid crystal display device.
A TFT (Thin Film Transistor)-method liquid crystal display module has been popularly used as a display device of a liquid crystal television receiver set, a personal computer or the like.
The liquid crystal display module is constituted of a liquid crystal panel which arranges a drain driver and a gate driver on a periphery thereof and a backlight which radiates light to the liquid crystal panel.
The backlight is roughly classified into the side-light backlight and a direct backlight. Recently, along with remarkable spreading of liquid crystal television receiver sets, large sizing and the acquisition of large screen have been in progress with respect to a liquid crystal display module used in a liquid crystal television receiver set or the like. In such a large-sized and large-screen liquid crystal display module, the direct backlight which can acquire high brightness is adopted.
As a light source of the direct backlight, a cold cathode fluorescent lamp (CCFL) has been dominantly used. Although the CCFL exhibits a long life time, a tube diameter of the CCFL is small and hence, along with the progress of large-sizing of a screen, it becomes difficult to adopt the CCFL as the light source. Accordingly, recently, to sufficiently cope with the large-sized large-screen liquid crystal display module, there exists a demand for the application of a hot cathode fluorescent lamp (HCFL).
The HCFL possesses a large tube diameter compared to the CCFL and exhibits high brightness and hence, the HCFL can realize a backlight for a large screen with the number smaller than the number of the CCFL. However, since the number of the HCFL is small, there arises a drawback on brightness irregularities.
As means which can efficiently reduce the brightness irregularities when the number of fluorescent lamps is small, there has been proposed a technique which arranges the fluorescent lamps non-uniformly to achieve the brightness distribution in which the center of the screen exhibits high brightness and a peripheral portion of the screen exhibits the low brightness.
Further, as another means to overcome the brightness irregularities of fluorescent lamps, there has been known an example which uses a light curtain (see following patent document 1).    [Patent Document 1] JP-A-2005-117023